Major Wire problem-- dash dissasembly. Need help. Ignition Mallory Unilite - Defender Source
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  #1  
Old August 6th, 2007, 09:52 PM
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Question Major Wire problem-- dash dissasembly. Need help. Ignition Mallory Unilite

I have some major problems with the ignition. The hot wire that goes to the coil (ignition wire) is grounded out somewhere when the key is off. It is actually still grounded out when the key is on. This is causing a power spike of sorts that is blowing every Mallory unilite module instantly. I traced the problem as the white wire that runs to the coil. It comes thought the firewall in the center and disappears. I need to find the short. It is still grounded even when I disconnect every fuse, and every connection from the ignition switch.

Another interesting thing that I noticed is that of the 4 connections on the ignition switch, 2 of them have the plastic melted off. I don't know if this is from the old bad switch, or if something else caused the switch to go bad.

Well... now that I explained what is wrong (or at least what I think is wrong) I need to know how to take apart the dash in the most time efficient way. I really don't want to have to disassemble the A/C. Is there anyone who has had a similar issue? Is the ignition switch supposed to be a ground on the + wire when it is off? Isn't that impossible? Anyway, maybe someone could help me figure this out.

(Side note) while diagnosing this problem I also found a short that was draining the battery... someone who replaced the windshield screwed threw the purple wire that powers the dome light.

Thanks Guys!

-Heath
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  #2  
Old August 6th, 2007, 10:13 PM
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Good news, the AC can stay completely in place and you can disassemble the dash enough to entirely remove the harness if you had to.

Taking the dash apart is not hard, there are just lots of screws and you need to keep track of where you put the fasteners. Also, you want to be gentle when you remove the instrument cluster, because the speedo cable can break off the speedo easily. Feed a little extra cable in from the engine compartment so that you have a little extra when you pull the cluster to disconnect the cable.

The dash is just several pieces stacked on top of each other. The lower dash (which the AC is attached to) is just a big air distribution plenum. It can stay put. The main harness follows the route you describe - in through the hole in the center of the firewall, and then over to the driver's area. The "tunnel" at the back of the tray is what conceals the wires.

The dash top comes off easily with several screws. The grab handle comes off one end (there is a screw behind the LR logo) and the cluster disassembles on the driver's side. The grey grill that the vent handles go through is the worst piece to get out. You have to flex and bend it a lot to pull it. Then the tray itself will pull free. Remove as many pieces as you need to get access to the harness. The way the wires snake through behind the cluster make it easy to understand how a short could develop, especially if someone has been in there messing for an alarm or some other hack mod.
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  #3  
Old August 6th, 2007, 10:21 PM
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It sounds like your problem starts with the wiring to the ignition switch itself. If the ignition switch wires are melted then you have some problems there. The "+" wire to the coil from ign. souldnt be grounded. I don't know about this problem on defenders but I have seen it in the past on DI. Most of the time repacing the ignition switch fixes the problem on the discos.

The "+" side of the coil should be hot with the ignition on position 2. The negative side of the coil should switch between "+" and "-" as you spin the engine over. I always use a test light to check this cause you can see the light flash as the engine spins(ground the test light and put the end of the light on the "-" side of the coil... If you have "+" 12v on the coil and the ground side flashes then the pick up in the distributor is working. If you aren't getting spark out of the coil wire at this point then the coil is probably the problem. If you are getting spark out of the coil but not to the plug wires at then you might need a cap or rotor button.

Hope this helps
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  #4  
Old August 6th, 2007, 11:46 PM
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This is your problem:



Good luck. I have an almost new ignition for sale if you end up needing it.
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  #5  
Old August 7th, 2007, 11:17 AM
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Thanks for the replies.

I do not have a wiring diagram to see what this looks like but I am wondering if the white wire is grounding out somewhere. I am talking about the white wire that runs with the white/red wire.

Does this wire branch off anywhere? does it simply run from the ignition switch to the + side of the coil? If that is the only problem I can just run a new wire and bypass the old one. That would be too easy though! I am sure that it is complicated somewhere. It is definitely grounded out. You can put a test light between + battery and the white wire that goes to the + coil when the truck is off and it goes on. It shouldn't be grounding ever should it? It should just be nothing when the ignition is off right?

Also... I just replaced the ignition switch... maybe the old one (which was bad) got so hot that the wire melted and grounded out! Also note that the ignition wire is still grounding even when it is not connected to the ignition and it is unplugged from the left side of the firewall (the brown plug with white and white/red wires). And that can't be right.

Anyone have a wiring diagram? I have a 1995 :-)
Thanks guys!

-Heath
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  #6  
Old August 7th, 2007, 12:22 PM
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Heath,

PM me your e-mail address. I will get you a wiring diagram.
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  #7  
Old August 8th, 2007, 10:20 PM
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Quote:
Originally Posted by Heath
Anyone have a wiring diagram? I have a 1995 :-)
Here is what the '93 manual says:
The ignition brings 12V to the coil.

Switch ignition to "On"
To test the low tension circuit, measure:
V1: between + and - of battery
V2: between ground (- of battery) and coil + from ignition
V3: between ground (- of battery) and coil - to amplifier
V4: between amplifier module case and ground

You should have:
V1: More than 11.5V
V2: 1 V max below value read in V1
V3: 1 V max below value read in V1
V4: 0 to 0.1 V

The circuit is: + battery to ignition key to + of coil to amplifier back to - of coil

If you think there is a short, disconnect the coil and the amplifier, see if you are still getting 12V at the wire coild plug (in case the amplifier is shot, it could short the circuit).

Anyway, what the manual says is:
Check incorrect reading(s) with chart to identify area of possible faults, i.e. faults listed under heading 'Suspect'.

V1 V2 V3 V4 Suspect
L OK OK OK battery discharged
OK L L OK Ignition switch and/or wiring
OK OK L OK coil or amplifier
OK OK OK H Amplifier earth

(OK: -> fine; L: -> Low reading; H: -> High reading)

If coil or amplifier is suspected, disconnect LT lead at coil, repeat V3. If voltage is still incorrect, fit new coil. If voltage is now correct, check LT lead, if satisfactory fit new amplifier.


HTH!
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  #8  
Old August 8th, 2007, 10:50 PM
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Here is the thing...
The voltage reads 0 when igntion is off and 12.9 when it is on.
It looks normal.

However, it is grounded when it is off. If you take a test light and put it between the + post of the battery and the + side of the coil ignition wire it will light up. It shouldn't light up at all. It shouldn't be grounded and have current going through it. That can't be right. It is touching ground somewhere.

I am so confused with this thing.

I am going to fiddle with it a bit more.

Maybe if that white wire is touching the firewall or if melted or something.

Maybe I can just run a new wire from the ignition switch to the coil.

I am trying to figure out if it has to connect anywhere else. That way I wouldn't have to rip the whole thing apart.

Thanks for all the help guys!

-Heath
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  #9  
Old August 8th, 2007, 11:00 PM
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Why not try this: disconnect the old wire and run a new wire between the switch and coil but don't bother routing it through the firewall just yet. Just run it though the open hood and driver's window, just to see if that fixes things.
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  #10  
Old August 9th, 2007, 10:30 AM
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Quote:
Originally Posted by Heath
Here is the thing...
The voltage reads 0 when igntion is off and 12.9 when it is on.
It looks normal.

However, it is grounded when it is off. If you take a test light and put it between the + post of the battery and the + side of the coil ignition wire it will light up. It shouldn't light up at all. It shouldn't be grounded and have current going through it. That can't be right. It is touching ground somewhere.
In your test, your light is the one acting as the ignition-turned-on element in the picture..... You have to use a voltmeter (or ohmmeter depending on what you want to measure, right? ;-) ) to be sure. Currently, you are just verifying that the amplifier is working (well... I don't know much about amplifier, so I am assuming the amplifier let current go through it).

Did you try to disconnect the wire coming from the ignition to the coil?
If you turn the ignition on, then on the "coil side" of the wire you should have 0V (or a very low value) if it's grounded (alternatively, you can use a ohmmeter to measure the "ignition" to ground path with the ignition off, should not be "infinite" if the wire is shorted).
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  #11  
Old August 9th, 2007, 11:44 AM
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I am a little confused.
I don't have an amplifier; just an internally resisted coil and a mallory unilite distributor.
I did away with the bosch system and had this running for quite some time until the ignition switch started acting up.

Everything is disconnected.

I have the white wire which runs from the ignition switch to the coil disconnected from everything. It is disconnected from the ignition switch and from the coil. Now that white wire is grounded. Also the white/red wire that comes from the ignition switch is similarly grounded. Meaning that if I take a light or a voltage meter or anything and connect the red to the + battery and the - to the white or white/red wire, it will show full battery voltage.

Is it possible that it is supposed to be this way?

I know that if I put a mallory unilite module in the distributor it will blow out before there is even a key turned on. I have tested them as per the mallory unilite test (for the optical sensor). These units just blow out as soon as I put them in.

I am wondering if the white wire and/or the white/red wire that come off of the ignition switch are supposed to read as a ground when the ignition is off? Maybe some relay somewhere does this? Maybe that relay is what is causing the problem with the unilite modules?

Thanks everyone for all of your help!

Another thing that is interesting is the absence of a relay in the fuse box next to the two yellow relays (on the right). Is there supposed to be a relay here? There are wires running out of the back of it, but there has never been one, at least not since I have owned the truck.

My ignition is pnwnd by Lucas.. strikingly similar to the name Lucifer.

Thanks again everyone!

-Heath
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  #12  
Old August 9th, 2007, 12:29 PM
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Quote:
Originally Posted by Heath
I don't have an amplifier;
Good that make it easier to troubleshoot then!
Quote:
Originally Posted by Heath
I have the white wire which runs from the ignition switch to the coil disconnected from everything. It is disconnected from the ignition switch and from the coil. Now that white wire is grounded. Also the white/red wire that comes from the ignition switch is similarly grounded. Meaning that if I take a light or a voltage meter or anything and connect the red to the + battery and the - to the white or white/red wire, it will show full battery voltage.

Is it possible that it is supposed to be this way?
Don't know, let's find out:

Ignition switch colours:
Position 1 - brown
Position 2 (key-in) - white/purple, brown
Position 3 - white/orange
Position 4 - white/red
Position 5 - white

So I'd guess those wire should only have 12V applied to them when the key is in that position, right?
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  #13  
Old August 9th, 2007, 05:01 PM
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That sounds right.

Only thing that doesn't make sense is that position 5 is "ignition on" and position 4 is "start" with that setup.

In other words, the white wire goes to the ignition, not the starter so it must go on position 4.

I am so confused.

I am trying to find the source of the power spike that is shorting out the unilite.
I think I might have to bite the bullet and get an electrical expert to solve this for me... if my truck ever wants to see the pavement, dirt or rocks again.
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  #14  
Old August 9th, 2007, 05:13 PM
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Quote:
Originally Posted by Heath
That sounds right.
Only thing that doesn't make sense is that position 5 is "ignition on" and position 4 is "start" with that setup.
In other words, the white wire goes to the ignition, not the starter so it must go on position 4.
I am so confused.
Could be a typo in the workshop manual...... That would not be a first (someone would have to check their truck to confirm/deny the exact color of the wires).

Quote:
Originally Posted by Heath
I am trying to find the source of the power spike that is shorting out the unilite.
I think I might have to bite the bullet and get an electrical expert to solve this for me... if my truck ever wants to see the pavement, dirt or rocks again.
As far as I know, not too many things can create "power spikes", definitely not a short (would have the effect the other way around).
- bad ground
- coil (if someone the coil was able to push power back to the input? Never heard of that)
- alternator (if the regulator is not in perfect shape, that will happen)
- any other large capacitor/motor(?) type equipment. Do you have an amp in your truck?
Unless the short is between the unilite and the ground of course.

I'd say to do what Chris said: if you suspect that a wire is shorted, disconnect it and bypass it by another wire and see if that changes anything.
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Quote:
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  #15  
Old August 9th, 2007, 05:27 PM
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I will try.
Problem is that every time I pop another unilite module it costs time and money.
I think there is some kind of device that lets you locate shorts... someone described it to me.
It pops and pops louder when you get closer to the short on a frame...
Has anyone heard of that tester?
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  #16  
Old August 9th, 2007, 05:37 PM
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Quote:
Originally Posted by Heath
I will try.
Problem is that every time I pop another unilite module it costs time and money.
I think there is some kind of device that lets you locate shorts... someone described it to me.
It pops and pops louder when you get closer to the short on a frame...
Has anyone heard of that tester?
An ohmeter that would show that the resistance value decreases as you are getting closer to the short?
Maybe there are properties of using AC when looking for shorts? (ohmmeter uses DC)
Any chance that you can find a "device" that would simulate the unilite (so that you not blow one up everytime you try something)?
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I have an ex MoD and an ex wife. The two no longer conflict with each other.
Quote:
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  #17  
Old August 9th, 2007, 05:51 PM
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I am pretty certain that it has to do with the ignition switch going bad.
The truck was turning on and off and I had to giggle the key to keep it running on the highway.
I drove it like that for too long I guess. Could this on and off have heated up the wires and made them melt into the firewall thus grounding out?

I do have a radio/cd player, but no amplifier, just the built in one. I have a winch, and an ARB compressor, but I have them disconnected (to deal with this problem).
Maybe it is a bad ground?

Where is the proper location for grounding the vehicle?

Maybe it is rusted, like everything else not aluminum.

Follow-up Post:

Ha ha...
Yes. The unilite.
At malory they stand behind their POS.
They pop at the slightest inperfection.
Nothing else could be that delicate.

But I do know this... they pop before I even try to crank it.
I ran the test on it (by placing a business card in between the optical sensor to change the voltage reading at the coil). It tested bad or popped, even before I tried to start the truck.

Which means to me... it is not the starter or the alternator.
It is the fact that the white wire is grounded out somewhere...
Can someone do a simple test for me?

Take your cluster out and do the following. Pull off the white wire at the ignition switch and over on the left side of the firewall (it is a brown plug with two wires under the heater). See if it is a ground (with the ignition off).

Also check the white/red wire and the white/orange wire.

Maybe they are supposed to be a ground when the ignition is off?

Maybe I am fighting the wrong battle?

Maybe it is something as simple as a bad relay somewhere?
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  #18  
Old August 9th, 2007, 06:03 PM
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Quote:
Originally Posted by Heath
Where is the proper location for grounding the vehicle?
The WSM says that there is:
- one ground connection from the engine wiring harness that in on the firewall (almost top center of the firewall, slightly toward the passenger side).
- one ground from the engine to the frame rail on the driver side
- if I remember correctly, there is a big ground connection between the frame rail and the gearbox

Funny enough a diagram shows that the starter relay is actually powered by a White-Red wire (Position 5?), that the Position 4 wire is white and that the Position 3 is White Orange.
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I have an ex MoD and an ex wife. The two no longer conflict with each other.
Quote:
it is not hoarding it is selective collecting
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  #19  
Old August 9th, 2007, 06:23 PM
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I have a few extra cables (from winches that died)... I am sure I can fab up some nice ground cables real quick and make double shure.

I guess the workshop manual was written by a few different guys... one color-blind.
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  #20  
Old August 10th, 2007, 12:10 AM
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Why don't you add another relay in the circuit that powers the distributor. Power the relay from a new source and use the old signal to engage the relay. That way you can at least prevent the damage to it. removing the dash to inspect your harness is probably a good idea as well. Take it down as far as Buck did and check all relevant wires to/from ignition switch.

Lucasfer is a son as well.
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